In manufacturing environments, passive indicators, such as cones, flags or signage, have been employed to alert individuals on a blind-side of an operation involving a tool with an operational path that may penetrate or pass through a barrier (e.g., airplane skin). Such passive indicators depend upon visual contact from an individual, but when an individual does not perceive the passive indicator the purpose is defeated. For example, an individual may be distracted by a cell phone, caught up in conversation, staring at the ground or stepping backwards. Subsequently, the individual may inadvertently pass into a working field into which the operational path of the tool extends.